Purcell principle

The Purcell principle is a United States judicial doctrine that cautions federal courts against changing election rules close to polling day, when doing so risks confusing voters or disrupting election administration. In 2026 the Supreme Court used it to keep Missouri on its 2022 congressional map for the November election.

The doctrine takes its name from Purcell v. Gonzalez, a 2006 Supreme Court case concerning Arizona voter-identification rules. Courts invoke it when they weigh the timing of injunctions affecting ballots, voter eligibility, district maps or election procedures.

Its significance lies in the tension it creates between correcting an allegedly unlawful rule and preserving settled arrangements for voters and election officials. The principle does not itself decide whether a rule is lawful; it guides courts on whether relief should take effect before an imminent election. Once ballots are in the post, as in Missouri, it weighs heavily against any change.